322a lab quiz 1 spring 06 key

322a lab quiz 1 spring 06 key - CHEMISTRY...

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Unformatted text preview: CHEMISTRY 3223L -Apf%i—3T—%GGG -SPR;NG—2006 Wm WM mam—wwz BY BEBE 1. (8) 2.(12) Lab time 3.(12) T.A. 4.(12) 5.(10) 6. (6) TOTAL (60) This test comprises this page and six numbered pages. If a question says to answer in fewer than a certain number of words, DO SO. Deduction for wordiness. —1— 172‘ 1. (2) A 14/20 male (inner) standard taper joint (like those on your _ ‘ distillation apparatus) is made of glass 1.0 mm thick. Calcu- O ,4/ late its Inside Diameter (ID) at its narrow end. Pall—M w m T my a H —75~»:A')um 833%) C 19;,“ a)?“ rue/(M iwé? and! flwckww 2W) “M 2) W L . _ _ 2. ( A circular groove in a flat iece of material has OutSide Diameter = 12 mm, and both width and depth = 1.5 mm. Calcu— late the ID of a non—stretchable O-ring which will just fit. £0= (2A ~<1w~r))m = 7 W, 3. (2) Complete the following sentence, defining the boiling point \ a (in general) of a liquid, A. The bp of A is .. . M r“? “7% fmesz“C/‘ W37 -(JM/¢:ij(74m WA fle (.K.._.__———f"m’(/JWW{' Below is the distillation curve for a 100 g of a solution of L (lower boiling) and H. There is no azeotrope in this system. Inf ‘ I'll-III IIII-IIIIIIIIIIIIIIIIIIIIIII-II IIIIIIIIIIIIIIIIIIIIIIII-I-II=III-IHIIlIIIIIIIIIIII III-IIIIIIIIIIII I-Ijllulllllififlfi'll IIIIIIIIIIIIIIII .- III-I IIIIIIIIIIIII;IIIII III-III-IIIIIII'C;nut-IIIIIII .-.-II...-I...---.-------------.--'4‘-.-.----.-.--- IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII‘IIIIIIIIIIIIIII III-IIIIIIIIIIIIIIIIIIIIIIIIIIIIIKIIIIIIIIIIIIIIIII III-IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIHIII-IIIIIIIIIIIIII II IIIIII IIIIIIIIIIIIII‘ I IIIIII II I IIIIII IIIIIIIIIIIIILI I IIIIII IIIIIIIIIIIIII-IIIIIIII-IIII-IVIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIII'I-IFfiIII-IIIIIIIIIIIIIIIII IIII!!IIIIIII-I"T:::u—ulllIIIIIIIIIIIIIIIIIIIIIIII --—:__-u-------.-...I....----..----.-'.-‘..-....--I IIIIIIIIIIIIIIIIIIIIIII-IIII-IIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIII-IIII-III...III-IIIIIIIIIIIIIII-I III-IIIIIIIIIIIIIIIIIII-IIIIIIIIIIIIIIIIIII-III..-I_ IIIIIIII-IIIIIIIIIIIIII-III-IIIII-IIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIII-III-IIII-IIIIIIIIIIIIIII-I to 10330 mhfiitw 10 $0 90 [00 Below, circle one of the items arated by / in each set. From the curve, H's bp is / . most 84°, and the 55 original mixture was about 60 // 7O / 75 / 85 % L. flJ 7, -. l p 5. (2) Acetic Acid (AA), CH3COOH, has strong H-bonding in the liquid. (1) It has abnormally low enthalpy and entropy of vaporiza- tion; and (2) its vapor density corresponds to MW ~ double its formula weight. Correlate (1) and (2) using <15 words. Vfirfio/Z (4‘ W777 75;) AW (and? a; 0064 (4f)m va/ar'z'f”. 6. (3) A pure organic liquid containing C, H, and 0 shows strong C-H 1 absorption in the IR, but no other strong absorption above 1550 cm‘l. Name or draw two oxygen—containing groups of atoms N: excluded by this result. 7% "rm [2:0 a ~0H. 466;“ @V‘} " 611M M( f“ A/ (3) An aqueous solution containing 20.0 g isopropyl alcohol (IPA, “mfg .78) ‘s "salted out“. The upper layer weighs 16.0 g and is 85% IPA, based on its measured density. Calculate what rac ion the original 20 g IPA is in the upper layer. 2W” (We/emf ML kw lé-Ua KW 9‘; a 51 n (2) Compound C, MW = 108, is steam distilled when Pexternal = 760 torr. If P°W(ater) = 600 torr at the mixture's bp, calculate the mass ratio in the distillate; Mwwater = 18. SW 600M Duo-é“— % @6046”) c 9. (2) W(ater) and odorous cpd D are mixed. Two liquid phases exist at equilibrium-~one is 1.0 mole % D, the other is 5.0 mole 95 W. Assuming that in each phase, Raoult's Law applies to the AZ majority component and Henry's Law to the minority one, give mud/3f— Ptotal for the W-rich phase, in terms of P°w and P° . . D 0 W I w Ptot, W—rich phase = 7 7 +~ MW umc («fife/x 0-77 I“ 0.7.(‘C1‘7 l/I‘) 1va 10 (4)(a)(2) A Drying Agent forms only a 2 hydrate; the DA/DA-2W has rel humidity = 5.0%. For a 3—fold DA excess added to a 3 9 W per L Org Solv saturated soln, calculate the final W conc. 0 NW guid) = 3&/L Kaar WM' 2 (b)(2) For the solution above treated with a DA of capacity 0.20 9 W per 9 DA, calculate how much DA is needed to dry 600 mL W-satd C7’%9\ For this calcn, assume all the W is removed. I M. 400 “L wvaf/ 0! km a“ 'C Efg‘ “"4 - y .g A} 60.9.3; “a” mfijflrwm anal. /——" For cpd F, KVB/VA, (i.e , z) = 6. Calculate the fraction of F unextracted [FUE = 1/(1 + (z/n))n] for (a) use of B all at once, and (b) use of B so FUE is minimized. Take e3 = 20. (a) (2) n 2 (b) (2) A400 - ' #015 : (I‘M _____' - (9" r“ H"“V0 é)” (c)(2) For 2 > 6, the superiority of (b) to (a) (circle one choice)-- decreases. 12. (2) J has mp = 100°, and L has mp = 130°. The most probable mp for a mixture of 85% J and 15% L is (circle one answer)-- 98° 105° 115° 125° 135° 1! ,47( 5525‘» 600417 {32E1q,, 6LA4/Oikuzt. IV" I“ 13. (3) A certain sample X, of mp = 75-80°, is suspected to be either largely cpd M or largely cpd N (but could contain neither). A mixture melting point with pure M of mp = 82—83° is 68-69°; a mmp with pure N of mp = 90—91° is 79~82°. Tell what these 1 data say about the likely composition of X; give reasoning. ’W\ [0W M/L,~wua7u “ if Mummgflaa % A'fiqwt W,‘.¢ 14. (6) A solid sample comprises 10 g P and 5.0 g Q, Whose solubili— ties in a solvent S are independent. The solubility of each in no; S is 5.0 g per 100 g S. In cold S, P's solubility is 1.0 g per 100 g S; Q is four times as soluble. (a)(2) Calculate the minimum amount of S needed to keep all the Q in solution after cooling. Show calculation. ‘ Jahcéof 62 w: (1!! J $06”ij M (b)(2) Remembering that it is éLsirable to get the entire sample dissolved, calculate how much hot S one should use initially. leve who}: 444 MW) “4 ’0 F :1 M %J={ 7.005 [off c)(2) If the initial dissolution in hot S gives a colorless solution with some brown goo sticking to the flask walls, tell what one f(_( MI should do nex are EiworZ/l a}; gig/[2" w (m W 3 '/,,/i57’7§)flélucose (dextrose, grape sugar) has mp ~148°. Addition of 1 g water to 6 9 glucose depresses its mp to 95°. Restate these data in solubility terms; refer to a temperature, the nature of the solution (dilute, conc, saturated), and to solution [440‘ composition in terms of the mass ratio of lucose to water. gm») At 750, 4 (4,6? «In (% (flaw «:w m é‘tyémiw fiV-ywkq’zawCC47M/LM. -5- 16. (10) Recall the preparation of n-BuI: i "[0 acetone r_1-BuBr + NaI ——> n—BuI + NaBr “3 1?; IV" (V796 (a) (5) Suppose one starts with 5.48 g n-BuBr and Calcu— late what volume (in mL) of n-BuI corresponds to a 75% NZ“ Mg ,9, -. 9-” 2 0.04041 ._ M fl;- ufl‘r W11" (b) (5) Both t—Bu—Cl and n—Bu-Br react rapidly with NaI in ethanol, giving ~100% yields of NaCl and NaBr respectively. Explain the following in mechanistic terms, using <35 words total: (1) The rxn rate of t—BuCl is independent of [I'] , while that of n—BuBr does depend on [I'] , and (2) the yield of n—Bu-I is unchanged by even a high cone of t—BuCl in the same rxn soln. évgkyC/J‘, V-Mf‘ (W4?0\: ~ t’Wlfz/k fiwf ('wvvludz' 5411, MA I 6"» fl’Qq-‘gh M W Zfl/Wl/fl" C-f'O’f/ (diva/(v4 (UH-£4.- 17. (6) Note the data below: Reaction AG fiscal). (1) n-Bu-Br -——-> n-Bu+ + Br" + 178 (2) NaI ----> Na+ + 1' + 164 (3) Q—Bu+ + I' -——-> Q-Bu-I — 171 (4) Na+ + Br" —---> NaBr — 174.5 (5) NaCl ---—> Na+ + c1" + 183 (6) n—Bu—Cl ———-> Q-Bu+ + C1" + 185 (a)(3) Calculate {kaoverall for the reaction: n-Bu—Cl + NaI ————> n—Bu—I + NaCl, showing your calculation. Mfr/PW tflq'((* M4 1: ""_’ 536%": +Uac/ +(Yr Plé‘f ‘17] “IX; (b)(3) Given that Keq for the reaction of (a) above is highly favora— ble, tell why alkyl chlorides are worthless in a practical sense for making alkyl iodides by the process used in this lab. You need not do calculations but do refer to how a changes along the reaction path. £05 V3 £17 31‘5"“ @ 4 n—6q’f 1’ ...
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This note was uploaded on 10/06/2009 for the course CHEM 322A taught by Professor Singer during the Spring '08 term at USC.

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322a lab quiz 1 spring 06 key - CHEMISTRY...

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